Core for electromagnets



Sept. 27, 1949. C, F, MlLLER 2,482,860

CORE FOR ELECTROMAGNETS Filed Dec. 14, '1945 PARA MA 6'4/67/0 SHLL SHA a nv 6 am@ of Cop/2E@ @ma as of? orme-R MAH-19ML sf/A' .o /N a R//va :E .LG- 1 b 00,96 aF coMpasss-o /Msa A reo PA/er/ cz is ARMA TURE l1-LET... E

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HA R o CsA/NFR ARMA TURE SWW Patented Sept. 27, 1949 CORE FOR ELECTROMAGNETS Charles Frank Miller, Frederick, Md., assignor to Price Electric Corporation, Frederick, Md.'

Application December 14, 1945, Serial No. 634,965

1o claims. 1

The invention relates to improvements in electromagnets, and more particularly to encased cores formed of paramagnetic powders.

One of the objects of the invention is to provide a core having an interior cf insulated compressed powdered iron or other paramagnetic material which has been finely divided and then compressed in such a way as to obtain a high density and more or less complete insulation of the paramagnetic particles.

Another object of the invention is to provide a shading arrangement for a core made of paramagnetic powders.

Another feature of the invention resides in the provision of a core whose shaded end is slightly conical in form so as to cause the armature to strike the pole face at a single point or at a region of very small area.

Still another feature of the invention resides in the provision of a hard center for a core of powdered material so as to withstand the impact of the armature when the end of the pole is made conical to provide a single point of contact.

The invention will be more readily understood by reference to the accompanying drawing and the following detailed description.

In the drawings:

Fig. 1 is a side elevation of a portion of an encased core of powdered paramagnetic material shown as provided with a shading ring in one end thereof;

Fig. 1a is an end view of the same;

Fig. lb is a longitudinal section;

Fig. 2 is a view similar to Fig. 1b in which the shaded end of the core is made conical to provide a single point contact for the armature;

Fig. 3 discloses a further modification wherein the shaded end is provided with a hard center.

Referring to the drawings, reference numeral I denotes an outer shell which may be made of paramagnetic material, such as iron tubing, or it may be made of other material, paramagnetic or otherwise. Paramagnetic material, however, is preferred. The shell as shown is circular in cross section, but other shapes may be employed if desired, although a shell of circular cross section is for many purposes preferred. The shell may, however, be of any shape and may be seamless, cr with any variety of slots, seams or perforations. The primary purpose of the outer shell is to give the inner core mechanical strength, but it may also be used to give the core magnetic, electrical or mechanical characteristics.

The inner core, indicated at l l, is formed of innetic material which has been finely divided and then compressed in such a way as to obtain a high density and more or less complete insulation of the paramagnetic particles. The primary function of this interior is to reduce loss due to eddy currents when the magnetic flux in the core varies with time, as in the case of a pulsating or alternating ilux, but this type of interior may be used to give the core special electrical, mechanical or magnetic characteristics. This type of construction is found to give excellent mechanical control in the design of magnets and results in low eddy current losses in applications where the magnetic ilux varies with time.V

The core is preferably provided with a shading ring l2, which may be formed of copper, brass or other highly conductive material. The outer periphery of the shading ring preferably forms a tight fit within the inner wall of the shell.

In the case of an alternating current magnet the pull on the armature passes through zero twice during each complete cycle of the alternating current carried by the magnet coil. The function of the shading ring isto produce an outof-phase magnetic flux at the interface between the armature and the shaded end of the magnet core. This ux passes through the shading ring into the armature and returns through the encasing tube of the powdered iron core and thus completely encircles the shading ring. As a result of the phase difference between the local flux produced by the shading ring and the main ux the pull on the armature never becomes zero. As a result the force of attraction between the armature and the pole face does not pass through zero twice per cycle as in the case of the unshaded arrangements.

As shown in Fig. 2 the shaded end of the core (the pole face) may be turned or otherwise shaped so that a slightly conical end I3 results. This turned pole face serves to cause the armature to strike the pole face at a single point or at a region of very small area. With the armature indicated diagrammatically at i4 hinged in the conventional manner this arrangement is desirable for the purpose of reducing chatter of the armature when the magnetizing force, is periogil-,gy

sulated pressed powdered iron or other paramagthe purpose of illustration, but it will be obvious aceaeeo that numerous modifications and variations may be resorted to without departing from the spirit of the invention.

The hard center l of the pole face may be either of paramagnetlc material, such as iron, where the eiciency of the joint between the pole face and the amature is' important, or it may be of non-magnetic material serving to form a magnetic breaker where there is danger of sticking due to remnant magnetism at the pcini-I of contact. If of non-magnetic material the core may be either some hard metal of alloy, or may be non-metallic material such as carborundum or the like.

I claim:

1. 1n an electromagnet having an armature, a core for the electromagnet comprising a compact cylindrical mass oi finely divided insulated pressed powdered iron particles, one end of the cylindrical mass being shaped to provide a conical pole face to cause the armature of the magnet to strike the pole face at a region of very small area, and a hard center embedded within said core and extending beyond the conical pole face to provide a small region of contact and to withstand the impact of the armature.

2. A core for an electromagnet comprising an outer shell of paramagnetic material, an inner core of compressed nely divided insulated paramagnetic particles within the shell, and shading means embedded in the core at one end thereof comprising an insert of solid highly conductive metal closely itting within the outer shell adjacent one end thereof.

3. A core for an electromagnet comprising an outer shell of paramagnetic material, an inner core of compressed iinely divided insulated paramagnetic particles Within the shell, and shading means embedded in the core at one end thereof comprising an insert of solid highly conductive metal closely fitting within the outer shell adjacent one end thereof, said shading means comprising a copper ring.

4. A core for an electromagnet comprising a shell of paramagnetic material of circular cross section, compressed iinely divided paramagnetic particles within the shell, said core having a conical pole face, and a shading ring of highly conductive metal such as copper embedded within the core and closely tting within the outer shell at the pole end thereof.

5. A core for an electromagnet comprising a shell of paramagnetic material of circular cross section, compressed finely divided paramagnetlc particles within the shell, said core having a conical pole face, and a hard center embedded within said core and extending beyond the conical pole face to provide asmall region of contact.

6. A core for an electromagnet comprising a shell of paramagnetic material of circular cross section, compressed finely divided paramagnetic particles within the shell, said core having a conical pole face at one end thereof, a shading ring of highly conductive metal .such as copper embedded within said core and closely fitting within the outer shell at the pole end thereof, and a hard center embedded within said core and extending beyond the conical pole face to provide a small region of contact.

.7. A core for an electromagnet comprislngan outer shell oi paramagnetic material, an inner core of insulated pressed powdered iron within the shell, said core having a pointed pole face at one end thereof, a shading ring of highly conductive metal embedded Within said core and snugly iitting Within the end of the shell adjacentv said pointed pole face, and a hard center embedded within said core and extending beyond the conical pole face to provide a small region of contact.

8. A core for yan electromagnet, comprising a compact cylindrical mass of compressed powdered paramagnetic particles, said core having a conical pole face at one end thereof, and a hard center embedded Within said core having a pointed end forming the tip of said conical pole face.

9. In an electromagnet having a movable armature, an elongated core comprising a compact mass of ilnely divided paramagnetic particles, said core having a pole face at one end for engagement with said armature, and a hard center embedded within said core and projecting beyond the mass of particles to provide a point of contact with said armature.

10. In an electromagnet having a movable armature, an elongated core comprising a compact mass of inely divided paramagnetic particles, said core having a pole face at one end for engagement with said armature, and a hard center embedded within said core and projecting beyond the mass of particles to provide a point of contact with said armature, said hard center being composed of carborundum.

CHARLES FRANK MILLER.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 724,060 Thomas, Jr Mar. 31, 1903 874,908 Fritts Dec. 24, 1907 928,547 Schureman July 20, 1909 1,005,857 Lindquist Oct. 17, 1911 2,141,890 Weis Dec. 27, 1938 2,356,577 Fuschaldo Aug. 22, 1944 2,427,872 Newman Sept. 23, 1947 OTHER REFERENCES Bergtold, Ser. No. 343,083,`May 18, 1943, (A. P. C. Publication) 

